The pyramid is shown in the diagram below.
The pyramid is built from four congruent triangles and one square as the base
We have the side of the square, so the area is = 10×10 = 100
We need the height of the triangle to work out its area. We can find out by using the height of the pyramid and half of the length of the side of the square.
Using the Pythagoras rule
Height of triangle =

Area of one triangle = 1/2×10×12=60
Surface area of the pyramid = 100 + (4×60) = 340 square inches
We can let
a = 1/(x-1)
b = 1/(y+2)
and rewrite the equations as
2a - b = 10
a + 3b = -9
Using the first to write an expression for b, we get
b = 2a - 10
Substituting this into the second equation gives
a + 3(2a -10) = -9
7a -30 = -9 . . . . . . . . simplify
7a = 21 . . . . . . . . . . .add 30
a = 3
b = 2·3 - 10 = -4
Now, we can find x and y.
3 = 1/(x -1)
x - 1 = 1/3
x = 1 1/3 = 4/3
-4 = 1/(y +2)
y +2 = -1/4
y = -2 1/4 = -9/4
Then the desired sum is
x + y = 4/3 -9/4 = (16 -27)/12
x + y = -11/12
The appropriate choice is ..
c. -11/12
Answer:
D
Step-by-step explanation:
Answer:
I would say the answer is c